A technology for nondestructively measuring a viscoelastic medium is very important in a food industry field. If an elasticity of a food may be conveniently detected, a quality of the food will be better controlled. In addition, in a medical field, various chronic liver diseases (e.g., virus hepatitis, alcoholic hepatitis, nonalcoholic steatohepatitis, autoimmune liver disease) will lead to hepatic fibrosis and hepatic cirrhosis. An elasticity of a liver will change during hepatic fibrosis and hepatic cirrhosis. If the elasticity of the liver may be nondestructively detected, conditions of the liver disease may be monitored and estimated so as to take effective treatment in time.
Chinese patent (publication No. CN1674827) discloses a device and a method for measuring an elasticity of a human or animal organ. The device comprises an ultrasonic transducer probe, a position sensor, an actuator, and a controlled electrodynamic actuator that generates a transitory low-frequency impulse. The device uses an ultrasonic wave at an ultra-high pulse frequency to detect a propagation velocity of an elastic wave produced by the transitory low-frequency impulse generated by the controlled electrodynamic actuator in a viscoelastic medium. Therefore, the elasticity of the viscoelastic medium may be obtained using an intrinsic relationship between the propagation velocity of the elastic wave and the elasticity of the viscoelastic medium.
In the above device, the electrodynamic actuator drives the ultrasonic transducer probe to generate a low-frequency vibration, thus introducing the elastic wave in the viscoelastic medium. The ultrasonic transducer probe transmits and collects the ultrasonic wave while generating a mechanical vibration, which may cause a reference point for collecting data of the ultrasonic wave to move. Therefore, before a further calculation using the data, a motion may need to be compensated. The device detects a motion of the ultrasonic transducer probe by the position sensor so as to compensate the motion of the ultrasonic transducer probe. Although the method may solve a problem of movement of the reference point by motion compensation, it may need extra calculation time. Meanwhile, because the position sensor needs to be mounted, a complexity and a cost of a system are increased.
In addition, the above device relies on manual operation, and consequently measurement results will be influenced by a pressure applied to the viscoelastic medium by the ultrasonic transducer probe and a verticality between the ultrasonic transducer probe and the viscoelastic medium in operation. In practical operation, an operator needs to determine whether the pressure applied to the viscoelastic medium and the verticality between the ultrasonic transducer probe and the viscoelastic medium are suitable empirically, so that detecting results will be easily influenced by subjective factors of the operator. Therefore, it is possible to cause large differences between results under operations of different operators or different operations of the same operator.
In addition, with the above device, a final result may be usually obtained by measuring the same position many times. Because the operator holds the ultrasonic transducer probe by hand during measurement, it is very difficult to ensure that all measurements are performed in the same position, which may also influence an accuracy of the result.